The Cell Biology and Histology Core (CBHC) is a critical resource to this PPG and will be used by all Projects. The CBHC will provide the projects with the following services: 1. preparation of cardiac progenitor cells (CPCs): isolation, characterization, and storage of CPCs from wild type and genetically modified mice, 2. preparation of stable lentiviral expressing lines of CPCs, 3. immunohistopathology: Preparation of histological sections for all projects, histopathology to assess gross and microscopic myocardial structure, fluorescent microscopic imaging of CPCs in heart section, analysis of vasculature. The CBHC will be located at the University of California, San Diego. The CBHC will house and maintain the equipment and provide fully trained staff for the Projects. It will provide the four projects with access to a wide variety of assays and analyses, including CPC isolation, sorting and characterization, assays of CPC function, and histopathology of heart samples obtained in vivo. CBHC services will also include isolation, maintenance characterization of CPCs from genetically engineered mice for the projects. CBHC will also expand and characterize the human CPCs isolated by Dr. Sussman for use by other projects. CBHC will ensure that all four projects will use CPCs that have been isolated, expanded and sorted the same way. This consistency is extremely important for the integration and comparison of results between the projects. The CBHC will also assist all the Projects with preparation of histological sections and histopathology to assess gross and microscopic myocardial structure, including the extent of fibrosis, quantification of chamber size and myocyte cross sectional area. It will also analyze heart sections for presence of apoptotic cells by TUNEL and anti-deaved caspase-3 immunofluorescence staining, and provide microscopic assessment of cardiac cell structure and signaling molecule localization via immunofluorescence of mouse heart sections. Finally, the CBHC will stain heart sections to detect c-kit positive CPCs plus markers of differentiation and proliferation, and prepare coronary vascular casts. Uniform preparation and analysis of histological sections from hearts are also important for consistent and comparable results between the four projects. RELEVANCE (See instructions); Heart muscle cells die when the tissue lacks oxygen, as occurs with a myocardial infarction (Ml; heart attack). Here we isolate progenitor cells that we believe could replace these dying cells and determine how to make them better able to heal the heart. We also examine the response of these cells within the heart and their effects on cardiac damage following Ml.